MariaDB's advantage over Percona (5.5) is the enhancements to Query Analyzer, which has largely been negated with the release of MySQL 5.6. As many workloads are now moving toward ACID based it makes sense to use the fork which concentrates on making InnoDB faster, more highly available and scalable and that fork is Percona and their XtraDB (a dropin replacement for InnoDB). Infact MariaDB use XtraDB in their fork, Percona use some of MariaDB features in their fork. Having used and tested all 3 forks (Stock, Percona, MariaDB) for many years I have found Percona to be the better one for *my* workloads.